AQA GCSE Biology B2.1
Cells and simple cell transport
Cell and Cell Structure
All living things made of cells. Small only seen with a microscope.
Most human and animal cells have the following:
A nucleus which controls the activities of the cell.
Also contains the chromosomes
A cell membrane which that controls the
movement of substances into and out of the cell
Cytoplasm which is where many of the
chemical reactions happen in the cell
Mitochondria which is where respiration takes place,
where energy is released during aerobic respiration
Ribosomes where protein synthesis takes place
In addition to these things plant and algal cells also have:
A rigid cell wall made of cellulose to
help keep the structure of the cell & strengthens it
A permanent vacuole filled with cell sap
Chloroplasts which contain chlorophyll
which is a green substance that
absorbs sunlight for photosythesis
Plant cells are different from
animal cells because they have
different functions
Bacteria & Yeast
Bacteria are v small
Bacterial cells have a cell membrane and cytoplasm surrounded by a cell wall
Bacterial cells do not have a nucleus so the genetic material is in the cytoplasm
Yeast is a single celled organism
Yeast cells have a nucleus, cytoplasm and a
membrane surrounded by a cell wall
Specialised Cells
Cells may be specialised to carry out a particular function
For example:
Sperm cells have a tail so that they
can swim and a rounded head so
that they are streamlined to aid
swimming
Root Hair cells
are long and thin
to absorb water
and nutrients
from the cell
Muscles cells have many
mitochondria as they
need a lot of energy
The structure of
a cell gives a clue
to its function
Diffusion
Dissolved
substances can
move into and out
of cells by diffusion
Diffusion is the spreading of particles
of gas or of any substance in solution
resulting in net movement from an area
of high concentration into an area of
low concentration
The difference in concentration between the two
areas is called the concentration gradient ~
Diffusion happens when particles move down the
concentration gradient
The larger the difference in concentration the faster the rate of diffusion
The shorter the diffusion distance the quicker it occurs
The larger the surface area for diffusion the faster it occurs
The smaller the particles the faster the rate of diffusion
Oxygen required for respiration passes through cell
membranes by diffusion